The objectives of the proposed research are: (1) to obtain a description of the ribonucleases of normal human serum and urine, including the number of species present, their electrophorectic properties, concentration, and catalytic properties; (2) to determine whether the elevated serum ribonuclease activity associated with various disease, especially cancer, is due to high levels of an enzyme(s) normally present in serum and urine or whether abnormal species are present; correlation of serum ribonuclease patterns with the histology and anatomical site of the primary tumor will be sought; (3) to determine which, if any, of the ribonucleases present in serum might originate in the formed elements of the blood; (4) to ascertain whether a carefully designed assay protocol will improve the reliability of elevated serum and/or urine ribonuclease activity as an indicator of specific malignant diseases in addition to multiple myeloma. The methods to be used include: (1) activity straining for ribonucleases following electrophoretic separation on polyacrylamide slab gels and measurement of activity in level by densitometry; (2) comparision of activity toward various substrates (RNA, biosynthetic polymer, etc.) using both activity staining and the more conventional ribonuclease assay which measures (spectrophotometrically) release of acid soluble material absorbing at 260 or 280 nm from a polymeric substrate.